Internal Hardware Design of a Microcontroller in VLSI Designers:

The Capstone Senior Project consists of designing some of the internal hardware components of a microcontroller in VLSI, using the software package L-EDIT. These components work together to create delays that can be used to run real time devices and trigger interrupts. The design is controlled by a 16-bit timer. The user can enter an 8-bit value into the accumulator and through the register controller, store the value in the specified register. The value in each of the four registers is compared to the lower 8-bits of the timer value in the comparator subsystem. The four comparators then output a single bit that is dependent upon whether or not the values are equal. Description: The design uses a top-down approach. Figure 1 shows the complete system level block diagram. The system has four main subsystems that need to be designed: the timer, the register controller, the register, and the comparator. The user inputs are the 8-bit value into the accumulator, the 2-bit register controller value, the reset to the 16-bit timer, and the clock. The user outputs are the 1-bit value from each of the four comparators, and the 1-bit overflow from the timer. Figure 1: System Block Diagram 316-bit timer subsystem: The timer is the main element of the project. As can be seen in Figure 2, the inputs to the system are clock and reset. The outputs are the lower 8 bits of the timer value, which input to the comparator subsystem, and the overflow bit, which is an external output. The timer operates as a 16-bit counter. After FFFFh has been reached, it sets the overflow bit high for one clock pulse and will restart at 0000h